In recent years, digital cameras have been developed greatly, and widely used, and various types of them have been supplied to the market. An electronic apparatus such as a digital camera is generally driven by a battery (such as a galvanic cell) from the viewpoint of portable property and mobile property, and in the case of an electronic apparatus driven by a battery, a voltage drop due to the use of the apparatus makes the apparatus operation unstable, therefore, an arrangement has been proposed in which, at the time of a drop of voltage, a voltage-drop display is given (Japanese Patent Application Laid-Open (JP-A) No. 9-130649), or another arrangement has been proposed in which, in the case when a battery has been consumed, a function for allowing the user to see how many more image-pickup operations are available (JP-A No. 2000-253303).
The battery of a digital camera is mainly consumed by displaying images during an image-pickup processor picked-up images on a monitor or flashing process or storing process of images in media such as memories. Moreover, in almost all digital cameras, the focusing operation control is carried out by auto-focusing, and power consumed by motor driving, etc., of the auto-focusing device is not negligible.
Here, in the method disclosed by JP-A No. 2000-253303, in order to consume a battery effectively with high operability while prolonging the battery life, there have been proposed a unit which determines the availability of a reproduction mode for displaying a picked-up image on the monitor or a flashing operation and a unit which inhibits the use of an auto-focusing unit in the case of a drop in voltage.
However, in the above-mentioned conventional art, when the battery voltage drops to a predetermined voltage, the auto-focusing operation suddenly becomes in-operative, causing the user difficulty in handling, and only the battery voltage forms a factor for determining the use of the auto-focusing unit, and no consideration is given to a case in which, in a cold place, the battery voltage suddenly drops due to degradation in the battery performance or a case in which an AC adapter that is not susceptible to a drop of power-supply voltage. Furthermore, the user is not allowed to switch the automatic focusing operation, and no consideration is given to a case when the user desires to increase the processing speed rather than saving the battery.